Wednesday, July 7, 2010

Technology Review: "A Guide to Recent Battery Advances"

Battery breakthroughs could lower costs and improve performance for electric vehicles and renewable energy storage--but commercializing these new technologies will be challenging.

Electric vehicles, hybrids, and renewable energy have at least one thing in common--if they're ever going to be more widely used, representing the majority of cars on the road or a large share of electricity supply, batteries need to get significantly better. Batteries will need to store more energy, deliver it faster and more reliably, and ultimately, cost far less. The specific ways batteries need to improve vary by the application, but in all these areas, researchers have been making significant headway.

Last week, MIT researchers led by Yang-Shao Horn , a professor of materials science and engineering and mechanical engineering, and Paula Hammond, a professor of chemical engineering, announced a new approach to high-power lithium-ion batteries, the type that's useful for hybrid vehicles or for stabilizing the electricity grid. High-power batteries accept and deliver charge rapidly. In hybrids, the goal is to supplement the gasoline engine, allowing it to run at its most efficient. The battery drives the car at low speeds for short distances and boosts acceleration, lowering demand on the engine. It also captures energy from braking that would otherwise be lost as heat. For the electricity grid, such batteries could buffer changes in supply and demand of electricity--something that's becoming more important as more variable sources of electricity are introduced, such as wind and solar power.

The MIT researchers demonstrated a new battery electrode, based on specially treated carbon nanotubes, that last for thousands of cycles without any loss in performance. Batteries made from these electrodes could deliver enough power to propel large delivery vans or garbage trucks, for example, without the batteries being too heavy to be practical. (The researchers need to increase the thickness of the electrodes for them to be practical in these applications.) Companies such as A123 Systems, based in Watertown, MA, have also developed very high-power lithium-ion batteries, and other academic groups and startups are developing carbon nanotube-based ultracapacitors, which store energy using a different mechanism than batteries that's particularly useful for high power and long life....MORE